Finding the Fourth Proportional to 1,420.89, 1,958.72 and 999.87

Step by Step Solution

1. Step 1: Write the proportion equation
   1,420.89 : 1,958.72 = 999.87 : x
2. Step 2: Convert to fraction form
   1,420.89/1,958.72 = 999.87/x
3. Step 3: Cross multiply
   1,420.89x = 1,958.72 × 999.87
4. Step 4: Simplify right side
   1,420.89x = 1,958,460.37
5. Step 5: Solve for x
   x = 1,958,460.37/1,420.89
6. Step 6: Final answer
   x = 1,378.33